/Engine/Source/Runtime/Core/Public/Math/RotationMatrix.h
Builds a rotation matrix given only a YAxis. X and Z are unspecified but will be orthonormal. YAxis need not be normalized.
static [TMatrix](API\Runtime\Core\Math\TMatrix)< T > MakeFromY ( [TVector](API\Runtime\Core\Math\TVector)< T > const & YAxis )